The poisoning mechanisms of different zinc species on a ceria-based NH3-SCR catalyst and the co-effects of zinc and gas-phase sulfur/chlorine species.

Low-medium temperature NH3-SCR technology has been applied for years in municipal solid wastes incineration (MSWI) to control the emissions of nitrogen oxides. Unlike coal-fired flue gases, the tail gas from MSWI contains high levels of heavy metals in fly ash, especially the zinc species, which may harm SCR catalysts. As such, in this paper, the deactivation mechanism of different zinc species (ZnO, ZnSO4 and ZnCl2) on the Sb-CeZr2Ox catalysts and the co-effects of zinc species and gas-phase pollutants (including SO2 and HCl) were investigated. The experimental results indicated that the deactivation rate of various poisoning zinc species was in the order of ZnCl2 > ZnSO4 > ZnO. Moreover, the interactions between zinc and antimony species would disrupt the structure of the Sb-Ce mixed oxides to decrease the redox ability, consequently suppressing the ammonia activation and NO adsorption. Furthermore, such damaging effects on catalyst structures would promote the formation of bulk-like sulfate species in the presence of SO2, resulting in a decreased mobility of surface oxygen species, which significantly decrease the sulfur resistance. However, the presence of HCl did not show an evident co-effect on the Zn poisoned sample owing to the limited coverage of the chlorine deposition.